Method and apparatus for imparting enhanced stretchability to paper



Oct. 30, 1962 o. HELAsTl 3,061,505

METHOD AND APPARATUS FOR IMPARTING ENHANCED "STRETCHABILITY TO PAPER Filed April 7, 1959 2 Sheets-Sheet 2 F'IG 7 FIGS United States Patent O 3,061,505 METHOD ANI) APPARATUS FR IMPARTING ENHANCED STRETCHABILITY T PAPER Olavi Helasti, Lohja, Finland Filed Apr. 7, 1959, Ser. No. 804,644 Claims priority, application Finland Apr. 16, 1958 2 Claims. (Cl. 162-109) It is of importance that papers, particularly sack papers, possess a high degree of stretch, i.e., that the papers may be pulled out to rgreatest possible length before the same break. Usually prior art has imparted high degree of stretchability to paper by passing the paper web without tension or draw through the drier section of a paper making machine, i.e., so the paper will contract freely. Also by adjusting the flow of pulp stock from the head box onto the forming wire the stretchability of paper has been improved. rIn addition to these methods there are still two different prior art methods for improving stretchability of paper. These two methods are based on crumpling of paper while it is in a suitable state of dryness. These methods, however, increase the stretchability of paper in the longitudinal direction of the web only. This invention has for its object to provide a method by means of which it is possible to produce longitudinally and laterally stretchable paper webs.

The basis of the invention is the discovery that while the paper web is still moist it is stretched by forcing it into small bags or the like -by means of suction. The method and apparatus of the invention will hereinafter be described more in detail with reference to .the exemplary embodiment shown in the accompanying drawing.

In the drawings 'I-IIG. l is a diagrammatic view of a paper making machine having therein an apparatus embodying the invention. FIG. 2 is a .front View, partly in section, of the apparatus of the invention. FIG. 3 -is a sectional view taken along line III-III of FIG. 2. IFIG. 4 is a sectional View taken along line IV-IV of FIG. 2. FIG. 5 is a top plan View of a mantle of the apparatus and lFIG. 6 is a sectional View along line VI-VI of FIG. 5. FIG. 7 is front view of another mantle and FIG. 8 is a sectional view along line VIII-VIII of FIG. 7.

The apparatus of the invention includes a tensioning roll which comprises a perforated cylinder 1 wherein is disposed a hollow shaft y2. connected to said cylinder by means of radially extending longitudinal partition walls 3 which divide the space interbetween the cylinder and the shaft into longitudinal cells 4. At the terminal ends of the cylinder are positioned the end walls 5 with apertures 6 leading into the cells 4. Within the shaft 2, at a spaced distance from the end Walls 5, are provided partition walls 7 having rigidly secured thereto the shaft bars 8 protruding from the end walls. The shaft bars are mounted in journal box 10 provided with bearings 9. The same are secured to the frame of the paper making machine by screw means 1\1 wherefore the same stay in place while the cylinder 1 rotates. The shaft bar on the one cylinder end is made so long that the same extends outwardly from the journal box. This shaft bar is coupled to the drive means imparting rotary motion so that the apparatus will rotate with the speed of the paper making machine.

Labyrinth packings 12 are disposed interbetween the end walls 5 and the journal boxes. At the top part of the right hand journal box 10 is provided a curved aperture 13 communicating v-ia the apertures in the end wall with the cells 4. This aperture 13 is so long that it communicates with three cells. At the bottom part of the right hand journal box is provided a circular hole 14 leading via the end wall 5 to a cell 4. When the ICC apparatus is mounted in place Ithe aperture 13 is connected to the suction system of the paper making vmachine by means of a line :provided with suction control means. The aperture 14 is connected to a compressed air source.

FIGS. 5 and 6 are illustrative in showing the cylinder mantle having spaced apart longitudinal rows of elongated apertures 15, said apertures in adjacent rows Ebeing in stepped relation to each other. The apertures are shaped so that the same have a first part 16 which narrows inwardly from the mantle outer surface and has an extension 17 of unvarying size. FIGS. 7 and 8 show a mantle with round holes 18. These holes are arranged in rows andthe holes of adjacent rows are side by side. The holes are shaped so that on passing from the outside inwards the same have a first funnel-like portion 19 and then as an extension thereof a cylindrical portion 20'.

FIG. l is illustrative in showing that the apparatus of the invention is positioned in the paper making machine so that the same will be interposed between the second press 21 and the finishing press Z2 so that the paper web will pass thereover. The apparatus is positioned in the aforementioned place so that a vacuum is produced in the uppermost cells and a pressure in the lowermost cell. From this it follows that as the web is being led to the apparatus it is caused to be drawn against the cylinder, to stretch slightly into the cylinder holes or apertures with the result that small bags are formed in the paper web. It is because of these bags that the paper will exhibit an enhanced stretchability. The perforations or apertures on the apparatus cylinder stay clean for the reason that each cylinder cell in its lowermost position is subject to the action of compressed air. When the paper web with the therein formed bags Iis passed into the ironing rolls it will be -found that the formed bags are hardly discernible inthe ready made paper.

As has already `been mentioned, the high degree of stretchability imparted to the paper web is determined by the therein formed bags.

The reasons for this are the following:

(l) The stretched portions of the web may contract freely because the flat portions of the web receive the contraction resisting tension lwhen the web is on the paper making machine.

(2) The flat portions of the paper web form a net- Stretch, percent breakin g length laterally longitumean in meters dinally value Untreated paper 6.0 2. 5 4.2 10.000 Treated paper o the invention. 8. 5 4. 0 6. 2 9.000

On the basis of the aforestated the stretchability of paper increases about 50% while the strength properties deteriorate by about 10%. In prior known methods .the strength properties may deteriorate by 50% even.

It will be seen from the `foregoing description that the invention provides a method whereby the stretchability of paper may be notably enhanced and also the stretchability laterally of the paper web may be improved. It will also be seen that in using the method of the invention the stretch properties of paper deteriorate appreciably less than in using prior art methods.

It is not absolutely necessary to yforce the bags into the paper web just at the stage interbetween the second press and the nishing press of a paper making machine for the main thing is only that the paper web is still moist when the bags are forced therein.

I claim:

1. A method of making paper suitable Afor paper bags, comprising pulling by suction spaced but closely adjacent portions of a moist stretchable paper web out of the plane of such web so as to stretch said suction-pulled portions to form in said paper web small adjacent projecting pockets thereby providing strong paper with great stretchability.

2. A method of making paper suitable for paper bags, comprising the steps of pulling by suction spaced but References Cited in the file of this patent UNITED STATES PATENTS 687,580 Schmidt et al. Nov. 26, 1901 689,400 Keeney Dec. 24, 1901 957,217 King et al. May 10, 1910 1,143,333 Tompkins June 15, 1915 1,224,650 Kitchen May 1, 1917 1,548,790 Lorenz Aug. 4, 1925 1,680,797 Lorenz Aug. 14, 1928 1,780,526 Kieffer Nov. 4, 1930 2,043,351 Pourness et al June 9, 1936 

1. A METHOD OF MAKING PAPER SUITABLE FOR PAPER BAGS, COMPRISING PULLING BY SUCTION SPACED BUT CLOSELY ADJACENT PORTIONS OF A MOIST STRETCHABLE PAPER WEB OUT OF THE PLANE OF SUCH WEB SO AS TO STRETCH SAID SUCTION-PULLED PORTIONS TO FORM IN SAID PAPER WEB SMALL ADJACENT PROJECTING POCKETS THEREBY PROVIDING STRONG PAPER WITH GREAT STRETCHABILITY. 